Backup for the heat pump: Maximizing self-consumption with AC ELWA 2

In the idyllic town of Ternberg, Upper Austria, the Szekeres family utilizes a 5 kWp south-facing photovoltaic system, complemented by a 0.8 kWp balcony power plant facing west. Despite these ideal conditions, the home's Vaillant heat pump with surface collectors has failed three times since the house was built in 2012, leaving the family without hot water for several days each time. These experiences prompted the owners to seek an alternative heating solution.

AC ELWA 2 for self-consumption and hot water security

Instead of opting for traditional, non-adjustable heating elements, the owner chose the AC ELWA 2 from my-PV. This linearly controlled photovoltaic heating solution can directly convert surplus solar power into heat. This approach not only maximizes self-consumption by using surplus solar power for heating but also ensures warm water availability by enabling backup heating with grid electricity if the heat pump fails. The AC ELWA 2 can achieve significantly higher temperatures than the heat pump, reaching up to 95°C, whereas the heat pump tops out at 50°C. This makes it easy to perform legionella prevention using solar power.

Optimized water heating

The Szekeres family primarily uses the heat pump for hot water in their four-person household. However, the heat pump frequently relies on grid electricity, even on sunny days. This is where the AC ELWA 2 comes into play: it uses surplus PV electricity to heat the water in the boiler, reducing the need for grid power.

Retrofitting challenges

The Vaillant 300-liter boiler lacked a heating element connection, complicating the direct installation of the AC ELWA 2. Owner Alexander Szekeres commissioned a custom flange with a specific bolt pattern to retrofit the heating element. This solution demonstrates that even under challenging conditions, photovoltaic heating retrofits are possible.

More than just a heating solution

Alexander Szekeres is confident: “The AC ELWA 2 has noticeably increased my self-consumption. On sunny days, it meets almost all of our hot water needs, reducing the heat pump’s operating time. This saves electricity, maximizes the use of solar energy, and prolongs the lifespan of the heating system.”

For him, the main advantage is the increased self-consumption, especially given the declining feed-in tariffs for solar power in Austria and Germany. “I’d rather make better use of my PV electricity for hot water preparation – it’s more efficient and saves costs in the long run,” Szekeres adds.